In the field of medical engineering, there are various known systems with which, via a flexible line, liquids can be withdrawn from patients or liquids can be fed to patients. The access to the patients is generally gained in this case by means of a catheter for insertion in an organ of the body or by means of a needle for puncturing vessels. During the examination or treatment, it has to be ensured that proper access exists to the patient. It is therefore necessary for the patient access to be monitored.
Proper access to the patient is also a particular prerequisite for the pieces of extra-corporeal blood treatment apparatus which have an extra-corporeal blood circuit. The known pieces of extra-corporeal blood apparatus include for example pieces of dialysis apparatus and cell separators which require access to the patient's vascular system. In extra-corporeal blood treatment, blood is withdrawn from the patient along a flexible arterial line having an arterial puncturing needle and is fed back to the patient along a flexible venous line having a venous puncturing needle. In acute dialysis at intensive care stations, what is used as a patient access is a central venous catheter in the patient's neck.
In spite of regular monitoring of the vascular access by the hospital staff, there is, basically, a risk of the puncturing needle slipping out of the blood vessel unnoticed or of a connection in a flexible line becoming disconnected. There are various known arrangements of different forms for monitoring the vascular access. These known monitoring arrangements generally rely on the safety devices which are provided as standard in the pieces of blood treatment apparatus and which trigger an immediate shutoff of the extra-corporeal blood circuit if there is not a proper vascular access.
What is generally used to connect catheters and flexible lines for making a patient access is the Luer connecting system which is well known in the medical field and whose connecting parts comprise an inner and an outer cone which form tapers. This connecting system is referred to as a Luer lock connection when, to secure the connection, the inner and outer cones are supplemented with a screw thread. Although Luer lock connections provide a very high level of safety, it has been found in practice that the connecting parts, if not properly handled or if used too often or if there are faults in their material, may become disconnected or micro-cracks may develop in the material. U.S. Patent Application Publication No. 2010/0228231 therefore proposes securing the connecting parts of a Luer lock connecting system against unintentional disconnection with an additional means of fixing the connecting parts.
There are known arrangements for monitoring a vascular access which have a device for detecting moisture to enable the escape of blood to be detected at the site of the puncture. The known devices for detecting moisture which are used in the known monitoring arrangements for the patient access take the form of a pad to be applied to the site of the puncture. The pad consists of an absorbent material in which is embedded a moisture sensor. Devices for detecting moisture which comprise an absorbent material which is applied to the patient's skin are described in, for example, International Patent Publication No. WO 2006/008866, U.S. Patent Application Publication No. 2005/0038325 and U.S. Pat. No. 6,445,304. The characteristic feature of the known pads is that the moisture sensor is embedded in the absorbent material and the absorbent material is applied to the patient's skin.
International Patent Publication No. WO 99/24145 describes a device for detecting moisture which has a housing, able to be closed off with a lid, in which a moisture sensor is arranged. Provided in the housing are apertures for the needles and flexible lines to pass through. It is a disadvantage that the housing containing the moisture sensor is relatively expensive to produce in large numbers and is relatively difficult to handle in practice.